1. Field of the Invention
The present invention relates to an image processing mechanism, and more particularly, to an interpolation method for image pictures when performing de-interlacing operations and image processing apparatus thereof.
2. Description of the Prior Art
As for the TV system recently, interlaced image formats are usually used for transmitting a TV signal (such as a NTSC TV signal) in order to acquire an improved frame quality by utilizing lower bandwidths. The principle is that a transmitter first scans odd scan lines 1, 3, 5, . . . , etc. to from an odd image field and scans even scan lines 2, 4, 6, . . . , etc. to from an even image field at a next time point. And then the two image fields are transmitted to a receiver, whereof the odd image field and the even image field are transmitted to the receiver repeatedly and alternately. The receiver (except the traditional CRT display apparatus) can perform a de-interlacing operation to transform the received interlaced image fields into progressive image fields to play the TV signal. The step of performing the de-interlacing operation should be cooperated with a motion compensation operation to interpolate pixels into a position to be interpolated in an image frame. However, when using the conventional motion adaptive mechanism to perform the de-interlacing operation and the motion compensation operation to improve image frame quality, the image objects moving in a high frequency in the original image frame are mostly unable to be interpolated effectively (such as the vertically moving caption in frames, that is to say the horse racing light caption).
In addition, due to the vertically moving caption usually having quite a lot of non-smooth edges (i.e., the letter line section of the horse racing light), a clear image frame can't be generated for the users if the conventional motion adaptive mechanism is directly used for performing the de-interlacing operation and the motion compensation operation. One of the conventional motion adaptive mechanism directly uses the information decoded by Moving Picture Experts Group standard or the information of Discrete Cosine Transform to perform the motion compensation operation, whereof its technology content is referred to the related description in the TWN patent No. 200514443. As for the image data that are not decoded by Moving Picture Experts Group standard, the decoded information is unable to be obtained by using the abovementioned method. Thus the motion compensation operation cannot be performed accurately.